Method of lowering the sulfur content of coal



Jan. 19, 1965 P. X. MASClANTONlO METHOD OF LOWERING THE SULFUR CONTENT OF COAL Filed Sept. 21, 196].

COAL

FRESH FUSED I SALT MAKE-UP FUSED SALT TREA TMENT FUSED SALT AND DESUL FUR/ZED COAL DECANTER -12 FUSED SALT COAL DESULFUR/ZED I WASH WATER WATER AND SALT EVAPORA TOR -15 WASHER l3 PHILIP X. MASC/ANTO/V/O ATTORNEY to about 0.6 percent.

United States Patent 3,166,483 METHOD OF LOWERING THE SULFUR CONTENT OF CGAL Philip X. Masciantouio, Penn Township, Westmoreland County, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Sept. 21, 1961, Ser. No. 139,756 3 Claims. (Cl. 202-25) This invention relates to an improved method of lowering the sulfur content of coal intended to be made into metallurgical coke.

An object of theinvention is to provide an improved method of lowering'the'sulfur content of coal wherein the coal is treated with a fused salt at elevated temperatures without destroying its coking properties.

A more :specificobject is to provide a method of extracting both inorganic sulfur from coal in which coal particles are agitated in a fused salt bath at an elevated temperature for a brief period, the desulfurized coal particles are separated from the fused salt and washed, and the fused salt re-used.

In the drawing, the single figure is a schematic flowsheet which shows the steps of my method.

As the fiowsheet shows, I feed crushed coking coal and fused salt to a heated treatment vessel in a ratio of at least 4 parts by weight of salt to each part by weight of coal. The coal should be crushed to minus /2 inch or finer. The fused salt is one which produces a strongly alkaline reaction and melts at a temperature sufficiently low to produce no significant adverse effect .on the coal. Examples of suitable fused salts are NaOH, KOH, anhydrous sodium or potassium acetate, or mixtures of the foregoing. Lime, sodium silicate or common salt melt at temperatures which are too high for them to be used alone, but they can be added as diluents. I may also advantageously acid sodium metal to the fused salt. A suitable temperature range for the fused salt treatment is about 200 C. to 450 C. or preferably 300 C. to 350 C., since higher temperatures tend to destroy coking properties of the coal. I use the term fused salt in accordance with the definition recognized in high-temperature chemistry, that is, a molten state of primarily ionic compounds.

I agitate the mixture of coal particles and fused salt in the treatment vessel 10 for a period up to about 45 minutes. The fused salt reacts with sulfur present in the coal as iron pyrite (FeS or as organic sulfur to form an alkali metal sulfide (Na s or K S) which dissolves in the fused salt. In this manner I can lower the sulfur content of a typical coking coal from about 1.6 percent Such coal goes into a semi-fluid plastic condition in which the fused salt can reach the sulfur-bearing compounds, but retains suitable coking properties on cooling, provided the treatment is not prolonged beyond about 45 minutes.

Next I allow the coal particles to settle and I decant the fused salt therefrom. As illustrated in the flowsheet, I transfer the mixture to a separate decanter 12 for this purpose, but alternatively I can utilize the same vessel that I use for the first treatment. a The decanter is heated or insulated to maintain the salt in fused condition while the coal particles settle. I transfer coal particles rea covered in the decanter to a washer 13 and I return the fused salt from the decanter to the treatment vessel 10 for re-use, as the flowsheet indicates. I introduce clean water to the washer and thereby wash away salt from the surfaces of the coal particles and also cool the material to ambient temperatures. It is important to wash the coal substantially free of alkali metal compounds, since they are objectionable when coke made from the coal is used in a blast furnace. The washed coal goes to storage 3,166,483 Patented Jan. 19, 1965 "ice an evaporator 15, where I recover additional salt which about 5 percent by weight.

I return to the treatment vessel 10. I have not shown the individual pieces of apparatus I use in practicising the invention, since each per se is of conventional construction.

'As the fused salt repeatedly reacts with sulfur, its sulfur content of course builds up. Ultimately sulfur in the fused salt reaches a concentration at which the salt is incapable of extracting any more sulfur from carbonaceousmaterial because of equilibrium considerations. However, I have observed this equilibrium is reached only after the fused salt has a sulfur content of re-use the fused salt up to about twenty times before its sulfur content builds up to this value.

The following specific examples demonstrate how my invention may be practiced:

Example 1 I introduced 100 grams each of KOH and NaOH to a one-liter iron pot and heated the mixture to 300 C., at which temperature it was molten. I rapidly stirred the fused salt and slowly added 50 grams of minus 40 mesh Robena coal which had a sulfur content of 1.64 percent. I continued to stir the resulting melt for 45 minutes at 350 C., and thereafter decanted the fused salt from the coal particles and washed and dried the latter. The sulfur content of the coal after this treatment was about 0.60 percent, and the coal retained good coking properties. The yield of treated coal was about 45 grams The fused salt was ready for re-use.

Example 2 I repeated the procedure described in Example 1, except that I heated the salt to 400 C. and added 3 grams of'rnetallic sodium to the melt. I observed a vigorous reaction immediately after adding the sodium, whereupon I separated the coal particles. After washing and drying, the coal had a sulfur content of 0.60 percent, with a yield of 93 percent, and it retained its coking properties.

. Example 4 I introduced 200 grams each of KOH and NaOH and grams of lime to an iron pot and heated the mixture to 350 C., at which temperature it was molten. I added 100 grams of minus 40 mesh coal and stirred the meltfor 5 minutes. After the coal particles were separated, washed and dried, they had a sulfur content of 0.90 percent, with a yield of 86 percent and they retained good coking properties. a

From the foregoing-description and examples it is seen that my invention affords a simple and practical method of lowering the sulfur content of coal used for making metallurgical coke. I believe it is an altogether surprising result that coal can be heated to temperatures as high at 450 C. in a fused salt without destroying its coking properties.

While I have shown and described certain preferred embodiments of the invention, it is apparent that other For a typical coal I can 3,1 eases modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. A method of lowering the sulfur content of coking coal without destroying its coking properties comprising treating the coal for a period up to about 45 minutes in a molten bath of material selected from the group which consists of sodium hydroxide, potassium hydroxide, anhydrous sodium acetate, anhydrous potassium acetate, and mixtures thereof, the bath temperature being about 200 C. to 450 (3., whereby the bath material reacts with sulfur in the coal to form an alkali metal sulfide soluble in the bath, separating the coal particles from the bath, and re-using the separated bath material.

2. A method of lowering the sulfur content of coking coal without destroying its coking properties comprising agitating the coal for a period up to about 45 minutes in a molten bath of material selected from the group which consists of sodium hydroxide, potassium hydroxide, anhydrous sodium acetate, anhydrous potassium acetate, and mixtures thereof, the bath temperature being about 200 C. to 450 C., the ratio of bath material to coal being at least 4 to 1 by weight, whereby the bath material reacts with sulfur in the coal to form an alkali metal sul- K fide soluble in the bath, separating the coal particles from the bath, washing the coal particles substantially free of bath material, and re-using the separated bath material. 3. A method of lowering the sulfur content of coking coal without destroying its coking properties comprising agitating the coal for a period up to about minutes in a molten bath of material selected from the group which consists of sodium hydroxide, potassium hydroxide anhydrous sodium acetate, anhydrous potassium acetate, and mixtures thereof, the bath temperature being about 300 C. to 350 C., the ratio of bath material to coal being at least 4 to 1 by weight, whereby the bath material reacts with sulfur in the coal to form an alkali metal sulfide soluble in the bath, separating the coal particles from the bath, washing the coal particles substantially free of bath material, and re-using the separated bath material in the method until its sulfur content builds up to a concentration of about 5 percent by weight.

References Cited in the file of this patent UNITED STATES PATENTS Hickey Oct. 1, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,166,483 January 19, 1965 Philip XQMasciantonio It is hereby certified that err en't requiring correction and that th corrected below.

or appears in the above numbered pate said Letters Patent should read as Column 1,

line 17, after "inorganic" insert and organic Signed and sealed this 1st day of June 1965 (SEAL) Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD OF LOWERING THE SULFUR CONTENT OF COKING COAL WITHOUT DESTROYING ITS COKING PROPERTIES COMPRISING TREATING THE COAL FOR A PERIOD UP TO ABOUT 45 MINUTES IN A MOLTEN BATH OF MATERIAL SELECTED FROM THE GROUP WHICH CONSISTS OF SODIUM HYDROXIDE, POTASSIUM HYDROXIDE, ANHYDROUS SODIUM ACETATE, ANHYDROUS POTASSIUM ACETATE, AND MIXTURES THEREOF, THE BATH TEMPERATURE BEING ABOUT 200*C. TO 450*C., WHEREBY THE BATH MATERIAL REACTS WITH SULFUR IN THE COAL TO FORM AN ALKALI METAL SULFIDE SOLUBLE IN THE BATH, SEPARATING THE COAL PARTICLES FROM THE BATH, AND RE-USING THE SEPARATED BATH MATERIAL. 